Local area network systems have been devised and are now in use to allow such communication described above. Inherent in these systems are obstacles addressed and overcome in this present invention.
Maximum cable length between repeaters.
This problem results in part because of losses incurred in the coaxial cable or other transmission media. However, the protocol used to implement collision detection and avoidance is also a contributor. If, as in one leading network, signal collision is detected by a voltage shift, cable lengths must be limited, higher quality cable required, and repeating amplifiers used. This invention allows cable length increases without the use of repeaters or higher quality cable.
Use of installed cable.
Hundreds of millions of feet of coaxial cable are already installed for existing systems at a cost of between $3 and $10 a foot. Capitalizing on existing cable can reduce costs significantly as well as reduce system installation time. Protocols that require cable replacement are unattractive at best. This invention can utilize installed cable.
Communication efficiency.
All the time spent in signal collision, detection and avoidance detracts from the overall efficiency of the system, This invention reduces collision processing dramatically. Data compaction as implemented in this invention also contributes to efficiency improvement.
This invention provides a protocol not requiring an electrical collision detection scheme, thus reducing stringent Cable requirements. Additionally, collision probability is reduced by a time slot technique. This protocol permits less expensive cable, longer cable distances, and greatly minimizes time spent dealing with signal collision.